Adjuvants are generally known as substances that are added in crop protection sprays, e.g., herbicidal formulations or agricultural spray compositions, or to spray tanks used in the dispersion of same to improve activity of an active ingredient, e.g. a herbicide, that is also present in the crop protection spray or to improve application characteristics. Spray adjuvants are generally grouped into two broad categories: special purpose adjuvants and activator adjuvants. Special purpose adjuvants are typically know to widen the range of conditions under which a given crop protection spray is useful. The special purpose adjuvant may alter the physical characteristics of the spray solution. Exemplary special purpose adjuvants include compatibility adjuvants, buffering adjuvants, antifoam adjuvants, and drift control adjuvants. Exemplary special purpose adjuvant compounds include phosphatidylcholine, alkyl polyoxyethylene ether, methylacetic (acid), soluble polymers such as xanthum gum, rheology modifiers such as polyacrylamide (EDT Concentrate) and styrene butadiene latex emulsions. Exemplary commercial products include In-Place®, InterLock®, Bond®, LI700®, and Strikeforce™. Drift control adjuvants are employed to reduce or eliminate fine spray droplet particles (“fines” or “driftable fines”) that are formed when the agricultural spray composition is sprayed, e.g., from an aircraft or a ground sprayer. Driftable fines are commonly defined as droplets that are less than 150μ, e.g., less than 105μ in size (droplet diameter). By reducing or eliminating driftable fines, drift control adjuvants allow more of the deployed agricultural spray composition to reach the intended target substrate. Because driftable fines are reduced, less of the deployed agricultural spray composition drifts away and damages adjacent vegetation. Some typical drift control adjuvants include crop oil concentrates (containing 80 to 85 percent of synthetic oil, 15-20 percent of surfactants), vegetable oil concentrates (containing 50-80 percent of vegetable oils and 20 to 50 percent nonionic surfactant), oil-in-water micro emulsions, and water-in-oil invert emulsions (made) with petroleum or vegetable oils, surfactants and water.
The oil-in-water micro-emulsions and water-in-oil invert emulsions are known to be essentially solvents or emulsifiable oils and typically have lower molecular weights, e.g., from 275 g/mole to 350 g/mole. Oil-in-water micro-emulsions and water-in-oil invert emulsions often contain a petroleum or vegetable derived oil that is immiscible with water and a surfactant to emulsify the mixture to make the oil and water miscible. These emulsions, however, do suffer from several disadvantages. For example, micro-emulsion droplets may be too large to spray. Also, the micro-emulsion may become unstable and phase separate over a time. The surfactants are known to produce foam during mixing especially with certain herbicides such as glyphosates. These drawbacks make it difficult to use such emulsions with conventional spray equipment without agitation. And in the case of large size droplets, large volumes of adjuvant are required to cover the pest infested target area. With the application of large volumes of pesticides applied to foliage, damage can be caused due to the toxic effect on the foliage by overconcentration of the emulsifiers and/or oil in the large droplets applied.
Activator adjuvants are commonly used to enhance post-emergence active ingredient performance, e.g., herbicide performance. Activator adjuvants are known to increase activity, absorption into plant tissue, and rainfastness. Activator adjuvants can also decrease photodegradation of the active ingredient and also alter the physical characteristics of the spray solution. Activator adjuvants include surfactants, crop oil concentrates, nitrogen fertilizers, spreader-stickers, wetting agents, and penetrants. Although these conventional adjuvants may provide for some improvements in active ingredient and/or agricultural spray composition efficacy, the ability to reduce driftable fines is limited (often due to the high amount of surfactants that are necessarily used therewith). These high amounts of surfactants increase drift potential and increase phytotoxicity to the foliage. Some of the conventional adjuvants in particular have a limited effect on the median spray droplet size. In some cases, conventional adjuvants not only form greater amounts of driftable fines, but some of these conventional adjuvants also form greater amounts of very large droplets, e.g., greater than 730μ in size. In particular, soluble polymer based products such as polyacrylamide and xanthum gum are known to shift the entire distribution substantially to large droplet diameters and also increase relative span. The very large droplets may result in an agricultural spray composition that provides poor coverage due to rebound from the leaf surface, which in turn reduces the overall efficacy of the active ingredients. The soluble polymers also hydrate slowly and mix poorly, which leads to processing issues such as longer mixing times. And soluble polymers are also more susceptible to degrade under shear stress during application or pump transfer. Further, the required usage level for these adjuvants is often quite high, which results in unwanted phytotoxicity of the foliage due to the high surfactant concentration (as noted above).
In addition, some conventional drift reduction adjuvants have been known to have deleterious effects on the sticking and spreading of the agricultural spray composition on the intended substrate, e.g., leaf surfaces, which may result in reductions in the efficacy of the active ingredient and/or the agricultural spray composition as a whole. For example, some conventional drift reduction adjuvants can make the agricultural spray composition droplets evaporate or dry too quickly, which prevents absorption of the systemic herbicide into the leaf substrate. Also, some conventional adjuvants affect the surface tension of the agricultural spray composition such that spreading of the agricultural spray composition on the substrate, detrimentally, is limited.
Some vinyl ester-based polymer dispersions, e.g., stabilized polymer vinyl ester-based polymer dispersions, have been employed in a variety of applications including, for example, as binders for adhesives, paints and paper coating compositions. In these applications, the polymer dispersion may be used in combination with other components, e.g., plasticizers. In these cases, the polymer dispersions are present in higher concentrations, while the other components are present in lower concentrations. These concentrations are suitable for the respective application, but may not be suitable for different applications. While these polymer dispersions are known to be utilized with adhesives and paints, the use of the (vinyl ester-based) polymer dispersions in the crop protection milieu has not been contemplated.
The weight average molecular weight of these emulsions can range upwards from 250,000 g/mol to 400,000 g/mol. Importantly, these polymer dispersions differ significantly from the aforementioned oil-in-water micro-emulsions and water-in-oil invert emulsions, in both chemical composition and physical properties. For example, the oil-in-water micro-emulsions and water-in-oil invert emulsions have lower molecular weight oils and do not comprise polymers and/or the monomer precursors thereof, and, as a result, lack the defined structure of aqueous polymer dispersions. The weight average molecular weight of these emulsions can range upwards from 275 g/mol to 350 g/mol. Oil-in-water micro-emulsions and water-in-oil invert emulsions are not known to be used interchangeably with vinyl ester-based polymer dispersions.
In view of the shortcomings of conventional adjuvants, the need exists for new adjuvants that provide for improvements in overall agricultural spray composition efficacy, e.g., reductions in driftable fines and maintenance of the relative span of the droplet size.